Foam inhibited gear lubricant composition



United States Patent 3,033,786 FOAM INHIBITED GEAR LUBRICANT COMPOSITION Paul W. Vogel, Peter A. Asseff, and William M. Le Suer,

Cleveland, Ohio, assignors to The Lubrizol Corporation, Wicklilfe, Ohio, a corporation of Ohio N0 Drawing. Filed Mar. 28, 1957, Ser. No. 649,018

6 Claims. (Cl. 252-34.7)

This application is a continuation-in-part of applicants copending application, Serial No. 460,500, filed October 5, 1954, and now abandoned.

This invention relates to the foaming of mineral lubricants and in a more particular sense to the prevention or destruction of foam in such mineral lubricants.

The formation of foam or froth in a hydrocarbon lubricant is occasioned at least in part by the vigorous agitation of mixtures of air and the lubricant which inevitably occur in any effective system of liquid lubrication. Thus, in the lubrication of an internal combustion engine, whether it depends upon a pump or is effected by splash, the lubricant is vigorously agitated with air to such a degree as to provide a very favorable environment for the formation of foam. The case is much the same for gear lubricants where the lubrication involves an obvious violent agitation of the oil. in addition to the role which agitation plays in causing foam, the presence of one or more additives in present-day lubricants is a second factor which aids in the formation of foam. Such additives generally are quite polar and tend to increase the surface tension of the oil in which they are dissolved. This condition of increased surface tension enhances the tendency to foam.

The objection to foam in a hydrocarbon lubricant arises primarily from the fact that appreciable quantities of lubricant may be lost by overflow through breather or vent outlets. Such breather outlets are present in a crankcase for the purpose of allowing the escape of blow-by gases from the combustion chambers. Many axle-housing units likewise contain such breathing vents, and in such units which do not contain a vent the problem of oil depletion is replaced by the problem of oil working its Way past the seals and into brake drums, etc.

It will be seen that these problems are the result of the substantial increase, by foam and froth, of the volume of a lubricant above that which the crankcase or other reservoir is intended to accommodate. inasmuch as the stability of foam is enhanced by increased viscosity, the problem is more acute in gear lubricants than in other less viscous lubricants.

In many cases the foaming of a hydrocarbon solution or dispersion can be dissipated effectively by incorporation in the liquid .of a small amount of a dialkyl silicone polymer; i.e., a silicone. Such silicones are commercially available and are effective in remarkable small concentrations; viz., one to ten parts per million. In other cases, however, the use of a silicone does not afiord a completely satisfactory solution of a foaming problem. Such a case is exemplified by a lubricant which provides an acidic environment. In such an environment the effectiveness of the silicone as an anti-foam agent is gradually diminished until after a week or two its effectiveness is almost nil.

There has been disclosed in a copending application, Serial No. 460,499 filed October 5, 1954, and now abandoned, the combination of a dialkyl silicone polymer and an amine as an effective anti-foam agent. Such a combination is particularly effective in acidic media such as exist frequently in gear lubricants, its effectiveness persisting throughout a much longer period of time than was possible with previously-known anti-foam compositions.

It is a principal object of the present invention to pro- Patented May 8, 1962 vide an anti-foam composition which is adaptable for use in lubricating compositions.

Another object of the invention is the stabilization of the anti-foam properties of dialkyl silicone polymers in particular environments.

These and other objects are accomplished by the compositions of the present invention; which composition comprises in combination a mineral lubricating oil, a liquid dialkyl silicone polymer, and an amine carboxylate, i.e., an amine salt of a carboxylic acid. This composition is an effective anti-foam material not only in neutral and basic media, but also in acidic media. Furthermore, the effectiveness persists through a much longer period of time than has previously been possible in acidic media.

A description of silicones which may be used in the hereindescribed composition is included in US. Patents 2,416,503 and 2,416,504. They include principally the liquid polymerization products of the low molecular weight dialkyl silane diols. These materials, although quite insoluble in hydrocarbon liquids, are readily dispersible therein, and are thought to be effective by virtue of their low interfacial tension toward hydrocarbon liquids. Dispersions of these liquid polymeric products are quite stable and effective as anti-foam agents, even in the presence of a great number of types of other additives.

The amine carboxylate may be selected from a wide range of types of compounds which includes compounds prepared from aliphatic and aromatic amines as Well as aliphatic and aromatic carboxylic acids. The amines, likewise, may be primary, secondary or tertiary. The amine carboxylate may be added as such to the lubricant composition or it may be formed in situ in the composition as in the case where an amine and a carboxylic acid are added separately.

The amines from which the amine carboxylate salt may be prepared include as indicated both aliphatic and aromatic, as well as primary, secondary and tertiary amines. Specific examples of these include the following: isopropyl amine, n-butyl amine, amyl amine, diamyl amine, n-hexyl amine, 2-ethylhexyl amine, n-octyl amine, tertoctyl amine (2-amine-2,4,4-trimethyl pentane), decyl amine, dodecyl amine, didodecyl amine, hexadecyl amine, octadecyl amine, octadecenyl amine, methyl octadecyl amine, tributyl amine, ethanolamine, diethanolamine, triethanolamine, diisopropyl amine, O-octyl triethanolamine, N-octadecyl ethylene diamine, ethylene diamine, propylene diamine, N-methyl ethylene diamine, aniline, N-octadecyl aniline, dimethyl aniline, N-phenyl ethylene diamine, dihydroabietyl amine, as well as the various alkylene oxide reaction products with these and other amines. Of particular utility are the ethylene oxide and propylene oxide reaction products with dihy'droabiethyl amine and N-octadecyl ethylene diamine.

Carboxylic acids which are useful in the preparation of the amine carboxylate salts include both aliphatic and aromatic acids. Specific examples of such useful acids include the following: oleic acid, linoleic acid, caprylic acid, caproic acid, capric acid, nap'hthenic acid, sulfurized oleoic acid, sulfurized eleostearic acid, thioglycolic acid, glycolic acid, succinic acid, adipic acid, chloroacetic acid, alpha-chlorostearic acid, phenyl-stearic acid, lauryl-benoric acid, etc.

As indicated previously, the combination in a lubricant of a silicone and an amine is an effective anti-foam agent not only in neutral and basic media, but likewise is satisfactorily effective in acidic media. This is of especial significance in the field of gear lubrication, because many gear lubricant additives depend upon their acidic character for extreme pressure properties. Thus, many gear lubricant additives are sufficiently acidic to impart an acidic environment throughout the lubricant in which they are employed, even though they be used only in rela tively minute proportions. Furthermore, the quality and desirability of acidic additives of this type are such that a satisfactory gear lubricant for present-day use usually will require the presence of such an additive.

This fact, i.e., the presence in gear lubricants of an acidic environment, plus the previously noted facts; i.e., (1) that the silicones by themselves are less eifective as anti-foam agents in acidic media and (2) that the stability of foam is enhanced by increased viscosity, points up a critical situation which preceded the discovery of the composition of this invention.

The acidic gear lubricant additives which may be used in present-day lubricants include among others the acidic organic product obtained by hydrolysis of the reaction product of an alcohol and a phosphorus halide. Usually in such an instance the phosphorus halide is a phosphorus chloride, e.g., phosphorus trichloride, thiophosphoryl chloride, etc. Such acidic products are organic phosphites and phosphates, including the thio derivatives thereof. In lubricants which contain such acidic materials the anti-foam activity of a silicone additive is slowly diminished until after a Week or two it is almost completely dissipated. This phenomenon is illustrated by the observation that a gear lubricant which contained 0.1% of an acidic phosphite prepared by the reaction of 2.5 moles of 2-methylpentanol-4 with phosphorus trichloride followed by hydrolysis of the resulting product, and 0.004% of a dimethyl silicone oil prepared by condensation of dimethyl-silane diol and having a molecular weight of 25,000 showed no foam immediately after it was prepared, but after it had been stored at 150 F. for one week it showed 280 ml. of foam. The foam was measured by the following procedure, taken from A.S.T.M. test D-89246T:

A 180-ml. sample is placed in a IOOO-ml. graduated cylinder and heated rapidly to 200:5 F., then placed in a bath maintained at 200il F. When the oil sample reaches the bath temperature a current of air is bubbled through the sample at the rate of 94:5 ml. per minute for five minutes. The volume, in ml. of air foam then is measured immediately and recorded.

The same gear lubricant, containing 0.1% of an acidic phosphite and 0.004% of a dimethyl silicone oil as described above, showed an even greater volume of foam, 470 ml., after it had been stored at 150 F. for a second week. Inasmuch as a gear lubricant is used under conditions in which the temperature often far exceeds 150 F., it is apparent that this lubricant is quite unsatisfactory beyond the first week of use with respect to its foaming tendencies.

A considerably greater degree of permanence of antifoam activity is available from the use of the composition of this invention. This is indicated by the tabulated data shown below:

Volume of Foam observed after storage at 150 F. for- Lubricant 1 Wk. 2 wks. 3 wks. 4 wks.

As has been indicated earlier in this description, the alkyl silicone polymers are effective in extremely low concentrations. For the purposes of this invention, it is in certain instances sufiicient that as little as one part per million (0.000l%) of an alkyl silicone polymer be used. The amine carboxylate likewise is effective in quite low concentrations and the scope of the invention is to be construed as covering the use of amounts of amine carboxylates of the order of at least about 0.05%. These minimum figures are expressed numerically as percentages by weight.

The utility of small amounts of silicone is shown by the following data:

As is the case with virtually all lubricant additives, the novel composition described herein is handled most conveniently as a concentrate. This facilitates its storage and transportation, and also allows its ready dispersion into a final lubricant. In such instances, it is particularly convenient to have the silicone present in concentrations as high as 0.1% or more and the amine in concentrations up to two or three percent or more.

Other modes of applying the principle of this invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such be employed.

We therefore particularly point out and distinctly claim as our invention:

1. A relatively non-foaming gear lubricating composition which comprises in combination a major proportion of a hydrocarbon lubricating oil, from about 1 to about 1,000 parts per million of a liquid polymer of a low molecular weight dialkyl silane diol, from about 0.05 to about 3.0% of a hydrocarbyl amine salt of a carboxylic acid selected from the class consisting of fatty acids, sulfurized fatty acids and naphthenic acids, and from about 0.05 to about 1.0% of an acidic alkyl phosphite.

2. A relatively non-foamnig gear lubricating composition which comprises in combination a major proportion of a hydrocarbon lubricating oil, from about 1 to about 1,000 parts per million of a liquid polymer of a low molecular weight dialkyl silane diol, from about 0.05 to about 3.0% of an alkyl amine salt of a fatty acid, and from about 0.05 to about 1.0% of a monoalkyl phosphite.

3. The gear lubricating composition of claim 2 characterized further in that the fatty acid is oleic acid.

4. The gear lubricating compositon of claim 2 characterized further in that the alkyl amine salt is an octyl amine salt.

5. The gear lubricating compositon of claim 2 characterized further in that the alkyl amine salt is a tertoctyl amine salt.

6. The gear lubricating composition of claim 2 characterized further in that the alkyl amine salt of a fatty acid is the tert-octyl amine salt of oleic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,355,255 Zimmer Aug. 8, 1944 2,375,007 Larsen May 1, 1945 2,498,628 Cyphers et al. Feb. 28, 1950 2,563,588 Dixon Aug 7, 1951 

1. A RELATIVELY NON-FOAMING GEAR LUBRICATING COMPOSITION WHICH COMPRISES IN COMBINATION A MAJOR PROPORTION OF A HYDROCARBON LUBRICATING OIL, FROM ABOUT 1 TO ABOUT 1,000 PARTS PER MILLION OF A LIQUID POLYMER OF A LOW MOLECULAR WEIGHT DIALKYL SILANE DIOL, FROM ABOUT 0.05 TO ABOUT 3.0% OF A HYDROCARBYL AMINE SALT OF A CARBOXYLIC ACID SELECTED FROM THE CLASS CONSISTING OF FATTY ACIDS, SULFURIZED FATTY ACIDS AND NAPHTHENIC ACIDS AND FROM ABOUT 0.05 TO ABOUT 1.0% OF AN ACIDIC ALKYL PHOSPHITE. 